We shipped FinalizationRegistry in Workers: why you should never use it

Cloudflare explains the addition of FinalizationRegistry support in Workers for cleaning up WebAssembly-allocated resources, while advising against relying on it due to non-deterministic behavior and restricted I/O in finalizers. The post details JS–Wasm memory management pitfalls, the security analysis underpinning the feature’s enablement, and promotes Explicit Resource Management (using/await using with Symbol.dispose) as the preferred, deterministic approach, with FinalizationRegistry positioned as a last-resort safety net.